The present invention relates to an information reproducing method of reproducing information recorded on a recording medium such as an optical card.
Conventionally, as a write once information recording medium, an optical disk or card for optically recording information is known. When data is recorded/reproduced on/from such a recording medium, the data is generally managed for each file. For management of this file data, auxiliary data, i.e., a so-called directory is used. Normally, as directory information, file information such as a file name, the file length, a start track and the like is recorded in part of the recording medium. If a defect in part of the recording medium forms an inaccessible region, an alternation process is performed as relief to record the same information on a region (to be referred to as an alternative region hereinafter) in place of the defect region. Such an information recording method is proposed in, for example, Japanese Laid-Open Patent Application No. 61-243994, in which defect information is recorded with directory information.
However, in the above method, if a large number of tracks with recording errors exist in one file, all error track numbers cannot always be recorded in one directory which impedes the management of the file data.
The present inventor has previously filed an information recording method in Japanese Patent Application Laid-Open No. 5-240812 which solves the above problem. This method will be described below. FIG. 1 is a block diagram showing the arrangement of an information recording/reproducing apparatus used for the above information recording method. Referring to FIG. 1, a recording/reproducing apparatus 31 (to be referred to as a drive hereinafter) records/reproduces information on/from a write once optical card 1 serving as an information recording medium. The drive 31 is connected to a host computer 32 serving as a host controller, and records/reproduces information on the basis of an instruction from the host computer 32. A motor 37 loads the optical card 1 into the drive 31 by a conveying mechanism (not shown), causes the card 1 to move back and forth in an R direction by a predetermined drive, and removes the card 1 from the apparatus. A light beam radiating optical system 38 includes a light source and scans a light beam spot on the optical card 1 in recording/reproducing information. A photodetector 39 receives the light of the light beam spot reflected by the optical card 1.
An AF actuator 40 drives part of the light beam radiating optical system 38 to move the focusing position of the light beam spot on the optical card 1 in a Z direction, i.e., in a direction perpendicular to the surface of the optical card 1, thereby performing autofocusing (AF). An AT actuator 41 drives part of the light beam radiating optical system 38 to move the light beam spot on the optical card 1 in a Y direction. i.e., in a direction perpendicular to both the R and Z directions, thereby performing autotracking (AT). The light beam radiating optical system 38, the photodetector 39, the AF actuator 40, and the At actuator 41 intergally constitute an optical head 50. A driving motor 36 moves the optical head 50 in the Y direction to cause the light beam spot to access to a desired track on the optical card 1.
An MPU 33 incorporating a ROM and a RAM controls the card driving motor 37 and the head driving motor 36, and performs transmission and control of data under the control of the host computer 32. An AT/AF control circuit 34 receives a signal from the photodetector 39 to drive the AF actuator 40 and the AT actuator 41, thereby controlling focusing and tracking. In this case, the AT/AF control circuit 34 receives the output from the photodetector 39 to control the AF actuator 40 and the AT actuator 41, thereby controlling AF AT. The output from the photodetector is also supplied to a modulation-demodulation circuit 35. The modulation-demodulation circuit 35 performs demodulation of the read information and sends modulated signal to the MPU 33. The modulation-demodulation circuit 35 modulates the information signal sent from the MPU 33, drives the light beam radiating optical system 38 in accordance with the modulated signal to record the information, and at the same time, demodulates the data on the basis of a signal from the photodetector 39. The host computer 32 transmits/receives data to/from the drive 31, and instructs recording/reproducing of information for each data track of the optical card 1. The optical card 1 generally has an inherently high error rate. Therefore, when information with high reliability is required, an error correcting means is necessary.
The above conventional information recording method will be described below. FIG. 2 is a block diagram showing the recording surface of an optical card used for the above method. An optical card 1 has a data region 2 and a directory region 3. Sectors S-1 to S-18 include sectors verified as error sectors upon recording as represented by hatched portions in FIG. 2. Files F1 and F2 comprise a plurality of sectors, and the directory region 3 has directories D1 to D3. Addresses representing sector positions in the data region divided into a plurality of sectors are conveniently called physical addresses. The physical addresses are sequentially counted from a start address. In FIG. 2, the sectors S-1, S-2, and S-3 correspond to physical addresses 1, 2, and 3, respectively. In contrast, only sectors verified as normally recorded sectors are conveniently called logical addresses. The logical addresses are counted from a start address. In FIG. 2, the sectors S-1, S-2, and S-5 correspond to logical addresses 1, 2, and 3, respectively. The subsequent logical addresses are similarly defined.
In the above-described Japanese Patent Application Laid-Open No. 61-243994 or Japanese Patent Application Laid-Open No. 5-250812, information of a defective sector generated in recording data is recorded together with directory information. FIG. 3 is a schematic view showing the defective information in the directory information of information (files F1 and F2) on the optical card 1 shown in FIG. 2. The directory information D1 corresponds to the file F1, and physical addresses 3 and 4 are recorded therein as defective sectors represented as hatched portions. The directory information D2 and D3 correspond to the file F2. Physical addresses 9, 11, 12, 14, 16, and 17 are represented as hatched portions, and all of them are defective sectors. FIG. 3 also shows the correspondence between the physical addresses and the logical addresses.
FIG. 4A is a view showing the format of a user directory used for the above information recording method, and FIG. 4B is a view showing the format of a system directory. These directory formats will be described below. A header is used to identify the user or system directory, and DIRU or DIRS is written in ASCII codes. A system directory number is a serial number commonly used for the system and user directories. A user directory number is a serial number used for only the user directory. A start logical sector address and the number of logical sector managed represent the start logical address of a logical region managed by the directory and the size of the region, respectively. A start physical sector address and the number of physical sector managed represent the start physical address of a physical region managed by the directory and the size of the region, respectively.
A defect list represents defect information constituted by a first address of the successive defective address serving as the start physical address of defective sectors and the number of the successive defective sector. This recording method is very advantageous in that a smaller number of bytes are required for a burst defect. Defect lists 1 to 3 can be recorded in the user directory. Defect lists 1 to 11 can be recorded in the system directory. User directory data is recorded in only the user directory and is constituted by information such as a file name, a file size, and the like.
FIG. 5 is a flow chart showing a process for recording file data in the above method. For example, data of the file F2 having a capacity for four sectors shown in FIG. 2 is assumed to be recorded. Referring to FIG. 5, the host computer 32 issues a recording request to the drive 3,1 and the data of the file F2 is transmitted. The data is sent to the MPU 33 of the drive 31. The MPU 33 stores a start physical address and a start logical address in the internal memory prior to recording of the data (steps S1 and S2). In this example, as is apparent from FIG. 2, the start physical address is "9", and the start logical address is "7". The MPU 33 controls various portions to record the data in the objective sector at physical address 9 (S-9), and immediately reproduces the recorded data to perform verification (step S3).
When verification is ended, the MPU 33 checks to determine if the data is normally recorded (step S4). Since physical address 9 is a defective sector, as shown in FIG. 2, a verify error is detected. When the verify error is detected, the MPU 33 stores the defective sector address in the memory (step S8) and increments the objective physical address by one (step S9), and the flow returns to step S3. In step S3, the data is rerecorded at the next physical address 10, and verification of the data is performed. In this case, as shown in FIG. 2, since physical address 10 is a normal sector, no verify error is detected. The MPU 33 allocates a logical address to the normally written sector, increments the logical address by one for next data recording (step S5), and increments the physical address by one for next data recording (step S6). The MPU 33 checks if all of the data of the file F2 is recorded (step S7). If NO in step S7, the flow returns to step S3, and the same process is repeated. When it is confirmed that all of the data of the file F2 is recorded, the MPU 33 notifies the host computer 32 of an end of recording, and ends the recording process.
FIG. 6 is a flow chart showing the method of recording a directory in the above information recording method. The directory is recorded after all of the data of the file F2 is recorded. FIGS. 7A to 7C are views showing the contents of directories when these directories are recorded in accordance with the flow chart in FIG. 6. Referring to FIG. 6, the MPU 33 prepares a defect list and sector management information on the basis of the defective sector address, the start recording physical address, the end recording physical address, the start recording logical address, and the end recording logical address stored in the memory (step S1). Information such as the defective sector address in the memory is stored when information is recorded as described above. The defect list is prepared before recording of the user directory, and a maximum of three lists are prepared. The defect lists and the sector management information prepared at this time are shown in FIG. 7B. In FIG. 7B, for example, the start logical sector address is "7" and the start physical sector address is "9". In defect list 1, the first address of the successive defective address is "9" and the number of successive defective sector is "1". In defect list 2, the first address of the successive defective address is "11" and the number of successive defect is "2". In defect list 3, the first address of the successive defective address is "14" and the number of successive defect is "1". Since a maximum of three defect lists can be recorded in the user directory, a defect list with defective start address 16 is not prepared in FIG. 7B.
The MPU 33 records the user directory constituted by the defect lists and the sector management information shown in FIG. 7B on the optical card 1 (step S2). When all of the defect information and the sector management information of the file F2 are recorded in the user directory, the process for recording the directory is ended. More specifically, it is checked to determine if a defect list remains (step S3). If NO in step S3, the process is ended. In this case, as described above, a defect list to be recorded remains. Therefore, the defect list and sector management information to be recorded are prepared (step S4), and a system directory is recorded on the basis of this information (step S5). The MPU 33 repeatedly performs the process of steps S3 to S5 until no defect information exists in the file F2. When all of the data is recorded, the process is ended. FIG. 7C is a view showing the system directory recorded by this method. It is apparent that the remaining defect list and the sector management information about defective sector address 16 are recorded. In this case, since the number of remaining defective sectors is 1, only defect list 1 (the first address of the successive defective address is "16"; the number of successive defective sector is "1") is recorded, as shown in FIG. 7C. However, a maximum of 11 defects lists can be recorded in the system directory. FIG. 7A is a view showing the content of the user directory when the data of the file F1 shown in FIG. 2 is recorded. Since two defective sectors successively exist in the file F1, only defect list 1 (the first address of the successive defective address is "3"; the number of successive defective sector is "2") is recorded. The number of defect lists is less than four. Therefore, the defect list is recorded in only the user directory and is not recorded in the system directory. According to the above information recording method, when the defect information of file data cannot be recorded in the first directory, the remaining defect information can be written in the second directory. Since all of the defect information of the file data can be recorded, the file data can be managed without being impeded.
In the above information recording method, when the host computer designates a logical address to access the information recording/reproducing apparatus, it is necessary to read all directories and store the defect lists in the memory. A process for converting the logical address into a physical address so that the host computer can read the data will be described below with reference to FIG. 8. For example, a process for reproducing data at logical address 6 shown in FIG. 2 will be described below. Referring to FIG. 8, a defect counter Cnt for counting defective sectors is initialized to be "0", and a defect list number Ptr is initialized to be "1" (step S1). It is checked if the number of successive defect in the defect list number Ptr is "0" (step S2). If YES in step S2, it is determined that no defect list exists, and the flow advances to step S6. On the other hand, if NO in step S2, it is determined that a defect list exists. A value obtained by subtracting the defect counter Cnt (=0) from the first address of the successive defective address (=3) of the defect list is compared with given logical address 6 (step S3). In this case, Bad.sub.-- A(Ptr)-Cnt on the right-hand side in step S3 is a logical address corresponding to the next physical address of the defective sector shown in defect list 1. This is physical address 5 and corresponds to logical address 3. Since, in step S3, given logical address 6 is larger than logical address 3, the umber of successive defect of "2" of defect list 1 is added to Cnt (step S4), and the defect list number Ptr is incremented (step S5). The above process is a process for determining a region to which the objective physical region of regions divided by defect lists belongs. After the process in step S5 is ended, the flow returns to step S2, and the same process as described above is executed. In this case, since next defect list 2 exists in step S2, the process in step S3 is executed again. The current Cnt is "2", and the first address of the successive defective address in defect list 2 is "9". The right-hand side in step S3 thus becomes "7", and the flow advances to step S6 to calculate the physical address. Since Cnt=2 and the given logical address is "6", the physical address becomes "8".
As described above, when the logical address is converted into the physical address to reproduce data accessed by the host computer, the defect lists must be sequentially checked, and all the defect lists must be stored in the memory. For example, assuming that the number of tracks of the optical card is 2,500 and the maximum number of sectors in one track is 16, the maximum number of sectors in the optical card is 40,000 as a whole. Therefore, when a defect list is represented by a 2-byte number for the start defect sector address and a 2-byte number for the number of successive defective sector, i.e., a total of 4 bytes the maximum number of defect lists is 20,000 (=16 sectors.times.2,500 tracks.div.2) lists if a defect exists in every sector. Accordingly, the MPU must have a memory capacity of 80,000 bytes (80 kbytes), i.e., 20,000 lists.times.4 bytes. As described above, conventionally, when the defect lists are stored in the memory, a large memory capacity is required.